i use only a heat pad and it keeps it plenty warm on the hot side. i keep it set on either low or medium and i use a thermostat with it because my apt. tends to warm up during the day with the sun coming in the windows and it was actually getting too hot in the tank. i have a red infrared bulb that i plan to use in the winter only if i need it. otherwise the heat pad keeps it more than warm enough. it partially depends on what size tank you are using though--if your tank is really big you may need to use both the pad and the light together.